Image enhancement techniques are used to emphasize and sharpen image features for display and analysis. Many different video decoders may be used, e.g. H.264, MPEG4, WMV, VC1. In order to reduce the data transmitted in systems with limited bandwidth or to reduce storage requirements of video media like DVD, H.264, for example, takes advantage of statistical redundancies (spatial and temporal) in video signals. A group of picture's size and sequence is specified such that periodically an entire frame will be encoded completely using a Discrete Cosine like Transform (DCT). Such pictures/frames are known as intra-frames, and the blocks that form them intramacroblocks. All other frames are made up from a mixture of these and intermacroblocks. These are encoded using prediction methods that encode only the difference between the macroblocks and some reference macroblock in a previous or future frame.
Both intra and intermacroblocks are transformed using a 2 dimensional DCT like transform. The DC (mean luminance) level and low spatial frequencies dominate in most image content, so this transformation results in the compaction of most of the energy into just a few of the elements of the block. Coefficients in the DCT domain correspond to weights of different spatial frequencies, with increasing spatial frequency starting for the DC component at the position top left in the matrix and moving towards the lower right corner. This invention realizes that performing contrast enhancement filtering within each H.264 video decoder or other video decoder macroblock can be achieved by increasing the value of specific DCT coefficients corresponding to the spatial frequencies desired to be enhanced.
It is therefore an object of this invention to provide an improved video decoder system and method with video enhancement using direct contrast enhancement in the spatial/Transform domain.
It is a further object of this invention to provide such an improved video decoder system and method with video enhancement using direct contrast enhancement in the spatial/Transform domain simply applicable to existing video decoders.
It is a further object of this invention to provide such an improved video decoder system and method with video enhancement using direct contrast enhancement in the spatial/Transform domain.
It is a further object of this invention to provide such an improved video decoder system and method with video enhancement using direct contrast enhancement in the spatial/Transform domain which consumes low additional MIPS (million instructions per second) and low additional complexity.
It is a further object of this invention to provide such an improved video decoder system and method with video enhancement using direct contrast enhancement in the spatial/Transform domain which provides better video quality even at low bit stream rates.
It is a further object of this invention to provide such an improved video decoder system and method with video enhancement using direct contrast enhancement in the spatial/Transform domain which allows for individual user enhancement control.
The invention results from the realization that improved video enhancement using direct contrast enhancement in the spatial/Transform domain can be achieved with intramacroblocks by transforming the decoded intramacroblock output to a matrix of spatial/Transform domain coefficients multiplying them by the corresponding elements of an intramacroblock enhancement matrix to provide enhanced spatial coefficients and then transforming the enhanced spatial coefficients to the temporal domain to generate an enhanced decoded intramacroblock and can be achieved with intermacroblocks by multiplying the spatial domain intermacroblock coefficients from the entropy decoder with the corresponding elements of an intermacroblock enhancement matrix to provide enhanced spatial coefficients and transforming the enhanced spatial coefficients to generate enhanced decoded residual coefficients.
The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives.
This invention features a video decoder with video enhancement using direct contrast enhancement in the spatial domain including a transform circuit responsive to the decoder intrablock output for converting the decoded video intramacroblock output to a matrix of spatial domain coefficients. There is an intramacroblock enhancement matrix having a corresponding matrix of elements. A multiplier circuit combines the spatial domain coefficients with the corresponding intramacroblock enhancement matrix elements to provide enhanced spatial coefficients. An inverse transform circuit responds to the multiplier circuit for converting the enhanced spatial coefficients to the temporal domain to generate an enhanced decoded intramacroblock output.
In a preferred embodiment the video decoder may further include an intermacroblock enhancement matrix including a matrix of elements; a multiplier circuit for combining the spatial domain intermacroblock coefficients from the entropy decoder of the video decoder with the corresponding intermacroblock enhancement matrix elements to provide enhanced spatial coefficients to the inverse transform circuit of the video decoder to generate an enhanced decoded residual coefficient. The intramacroblock enhancement matrix and intermacroblock enhancement matrix may be of different rank. In the intramacroblock enhancement matrix and intermacroblock enhancement matrix the same spatial frequencies may have the same enhancement element. The intermacroblock enhancement matrix may have the same rank as the entropy decoder. The enhancement elements may be different for each of the enhancement matrices. The intermacroblock and the intramacroblock enhancement matrices may include a gain adjust circuit for varying the enhancement matrix elements. The gains of the gain adjust circuits may be different for the enhancement matrices. The gains of the gain adjust circuits may be the same for the enhancement matrices. The video decoder may be an H.264 decode. The intramacroblock enhancement matrix may have a rank of 8. The transform circuit may be an 8 rank DCT and the inverse transform circuit may be an 8 rank IDCT. The H.264 decoder may be base profile and the intermacroblock enhancement matrix may have a rank of 4. The H.264 decoder may be main profile and the intermacroblock enhancement matrix may have a rank of 4. The H.264 decoder may be high profile and the intermacroblock enhancement matrix may have a rank of 8. The transform circuit may be a DCT circuit. The inverse transform circuit may be a IDCT circuit. The inverse transform circuit of the video decoder may be integer transform circuit.
This invention also features a video decoder with video enhancement using direct contrast enhancement in the spatial domain including an intermacroblock enhancement matrix including a matrix of elements. A multiplier circuit combines the spatial domain intermacroblock coefficients from the entropy decoder of the video decoder with the corresponding intermacroblock enhancement matrix elements to provide enhanced spatial coefficients to the inverse transform circuit of the video decoder to generate an enhanced decoded residual coefficient.
This invention also features a video decoder with video enhancement using direct contrast enhancement in the spatial domain including a transform circuit responsive to the decoder intrablock output for converting the decoded video intramacroblock output to a matrix of spatial domain coefficients. There is an intramacroblock enhancement matrix having a corresponding matrix of elements. A multiplier circuit combines the spatial domain coefficients with the corresponding intramacroblock enhancement matrix elements to provide enhanced spatial coefficients. An inverse transform circuit responds to the multiplier circuit for converting the enhanced spatial coefficients to the temporal domain to generate an enhanced decoded intramacroblock output. There is an intermacroblock enhancement matrix including a matrix of elements. A multiplier circuit combines the spatial domain intermacroblock coefficients from the entropy decoder of the video decoder with the corresponding intermacroblock enhancement matrix elements to provide enhanced spatial coefficients to the inverse transform circuit of the video decoder to generate an enhanced decoded residual coefficient.
This invention also features a method of video decoding with video enhancement using direct contrast enhancement in the spatial domain including transforming the decoded intramacroblock output to matrix of spatial domain coefficients. The spatial domain coefficients are multiplied with the corresponding intramacroblock enhancement matrix elements of an intramacroblock enhancement matrix to provide enhanced spatial coefficients. The enhanced spatial coefficients are transformed to the temporal domain to generate an enhanced decoded intramacroblock.
In a preferred embodiment the method of video decoding with video enhancement using direct contrast enhancement in the spatial domain may further include multiplying the spatial domain intermacroblock coefficients from the entropy decoder of the video decoder with the corresponding intermacroblock enhancement matrix elements of an intermacroblock enhancement matrix to provide enhanced spatial coefficients; and transforming the enhanced spatial coefficients to generate enhanced decoded residual coefficients. The intramacroblock enhancement matrix and intermacroblock enhancement matrix may be of different rank. In the intramacroblock enhancement matrix and intermacroblock enhancement matrix the same spatial frequencies may have the same enhancement element. The intermacroblock enhancement matrix may have the same rank as the entropy decoder. The enhancement elements may be different for each of the enhancement matrices. The spatial domain may further include adjusting the gains of the enhancement matrices. The video decoder may be an H.264 decoder. The intramacroblock enhancement matrix may have a rank of 8. The H.264 decoder may be a base profile and the intermacroblock enhancement may have a rank of 4. The H.264 decoder may be a high profile and the intermacroblock enhancement may have a rank of 8.
This invention also features a method of video decoding with video enhancement using direct contrast enhancement in the spatial domain including multiplying the spatial domain intermacroblock coefficients from the entropy decoder of the video decoder with the corresponding intermacroblock enhancement matrix elements of an intermacroblock enhancement matrix to provide enhanced spatial coefficients. The enhanced spatial coefficients are transformed to generate enhanced decoded residual coefficients.
This invention also features a method of video decoding with video enhancement using direct contrast enhancement in the spatial domain including transforming the decoded intramacroblock output to matrix of spatial domain coefficients. The spatial domain coefficients are multiplied with the corresponding intramacroblock enhancement matrix elements of an intramacroblock enhancement matrix to provide enhanced spatial coefficients. The enhanced spatial coefficients are transformed to the temporal domain to generate an enhanced decoded intramacroblock. The spatial domain intermacroblock coefficients from the entropy decoder of the video decoder are multiplied with the corresponding intermacroblock enhancement matrix elements of an intermacroblock enhancement matrix to provide enhanced spatial coefficients; and transforming the enhanced spatial coefficients to generate enhanced decoded residual coefficients.